CHICAGO (CBS) A man who was arrested for having a gun Monday night said he purchased it from a man who illegally trafficked the firearm used to murder Chicago Police Officer Thomas Wortham IV in May, police said.

Sterling Alexander, 26, of the 7100 block of South Campbell Avenue, was booked into Cook County Jail Tuesday after being ordered held without bond, according to the website for the Cook County Sheriff’s Office. Alexander was charged with unlawful use of a weapon by a felon, possession of a stolen firearm and resisting arrest, police said.

About 8 p.m. Monday, officers were in the area of the 7100 block of South Campbell Avenue in the process of arresting Kevin Williams, 24, of the 1100 block of West 90th Street, for a weapons violation.

Alexander allegedly began interfering with the arrest apparently because Williams is an acquaintance. Investigators then began to focus on Alexander and they learned that he had a firearm under a mattress inside a home at the Campbell Avenue address. During questioning, Alexander told officers he had purchased the firearm from Quawi Gates, 27, of Chicago.

Gates, formerly of the 2100 block of West 71st Street, was sentenced to two consecutive 5-year prison sentences Wednesday, Aug. 25 in a federal court in Mississippi, according to a release from the U.S. Bureau of Alcohol, Tobacco and Firearms. Gates earlier pleaded guilty to two counts of aiding and abetting another to cause a federal firearms dealer to keep false records, according to the release.

Four guns purchased for Gates in Mississippi have been recovered in violent crimes in the Chicago area involving Gangster Disciple street gang members, according to the ATF release. One of the guns Gates illegally trafficked was used in the May 19 murder of Officer Thomas Wortham IV, who was gunned down in front of his parents’ Chatham neighborhood home in an apparent robbery attempt.

Two men – Paris McGee, 20, and Toyious Taylor, 29, were charged in Officer Wortham’s murder. A third suspetct, Brian Floyd, 20, was shot and killed on the scene by Wortham’s father.

Williams was charged with unlawful use of a weapon by a felon, possession of a controlled substance and armed habitual criminal, according to police. The sheriff’s website said Williams was booked into Cook County Jail on Tuesday also, but was ordered held on $250,000 bond.

It is not alleged that Williams’ weapon had any connection with Gates.

Alexander is scheduled to appear in court next on Oct. 12, while Williams will appear Oct. 27, the Sheriff’s website said.